1. Field of the Invention
The present invention relates to audio playback apparatuses that decode and reproduce audio data subjected to compressive coding.
This application claims priority on Japanese Patent Application No. 2005-320535 and Japanese Patent Application No. 2006-45153, the contents of which are incorporated herein by reference.
2. Description of the Related Art
Recently, a variety of coding and decoding techniques such as MP3 (MPEG Audio Layer-3) and AAC (Advanced Audio Coding) have been developed and widely used in audio playback apparatuses.
Game devices are designed in different concepts compared with CD players and broadcasting systems because of loop playback functions (or loop reproduction functions) in which prescribed portions of phrases of musical tunes or sounds are repeatedly played back and reproduced. Game devices frequently play back audio data subjected to compressive coding (hereinafter, simply referred to as compressive coded data) by way of loop playback functions. In the known audio technology such as MP3, an audio waveform of one phrase (constituted by a string of samples) is divided into a plurality of blocks, so that compressive coding is performed in units of blocks. Herein, a start point and an end point of a loop are set to a string of samples forming a block (hereinafter, simply referred to as a sample string). This raises a difficulty in smoothly and repeatedly playing back the sample string with respect to the loop defined between the start point and the end point without causing breaks. The loop playback can be realized by way of a method in which one phrase is divided into three sections, namely, a first section formed before the start point of a loop, a second section actually subjected to loop playback, and a third section formed after the end point of the loop, wherein compressive coding is performed on the first, second, and third sections respectively so as to produce three sets of compressive coded data. However, this method causes a problem in that, during the execution of the normal playback different from the loop playback, an unexpected break may occur in the playback of the sample string due to the transition of decoding from one section to the next section. Japanese Patent No. 3601473 teaches a technology regarding loop playback for decoding compressive coded data. This technology realizes the playback of audio data of one phrase without causing breaks; however, it does not realize the loop playback with respect to a desired section extracted from one phrase of an audio waveform.